Three Simple Ways to Test Your Soil

Four Season Garden: DIY Soil Tests and Reading the Weeds

What do you know about the soil in your garden? Knowing your soil type can help you determine what to plant and how to amend your garden to its best advantage. Three simple do-it-yourself tests can help you find out the texture, composition and pH (acidity or alkalinity) of your soil. By doing a 2-minute hand test, by assessing the texture of your soil in a jar, and by looking at the weeds that grow naturally in your garden, you can learn a lot.

Three Kinds of Soil

All soil comes from components of rock: sand, silt and clay. The kind of dirt you have in your garden depends on the proportion of each of these components.

• sand – coarser than silt; loose, drains water and nutrients quickly; heats up quickly.• silt – granular material between the size of sand and clay.• clay – fine grained rock material combined with clay minerals. Slow-draining; holds water and nutrients. Tends to have a lower soil temperature, making it difficult for plants to establish roots.

Loam, the most beneficial soil for gardening, has a mineral composition of about 40% sand, 40% silt and 20% clay. This combination of soil components holds nutrients and water, while draining well. Loam comes in various gradations—sandy loam, silty loam, loamy clay—each with a slightly different composition.

Soil pH—Acid or Alkaline?

Soil can also be acid (“sour”), neutral, or alkaline (“sweet”). The soils in coastal British Columbia, where evergreens grow in abundance, tend to be naturally acidic. On the pH scale, 7.0 is neutral, less than 7 is acidic, and greater than 7 is alkaline. Most vegetable garden plants grow best at slightly acidic or near neutral conditions (5.5 – 7.5).

Three Easy Soil Tests

You can easily assess the dirt in your garden with these simple methods:

1) Soil Hand Test – Does Your Soil Form a Ribbon?

The “feel” of your soil and the way it handles can help you determine its composition.

This ribbon of soil pressed between the first finger and thumb measures less than 2 cm at its break point. The length (<2.5 cm/1 inch), plus its gritty feel, indicates sandy loam.

• Rub a bit of moist dirt between your fingers and observe how it feels.

• Now, squeeze the moist ball of soil out between your finger and thumb. Continue until the “ribbon” of soil breaks. Measure the length of the ribbon. Refer to the table below for results. If you can’t form a ribbon at all, it means you have sand.

How to Read the Soil Hand Test

How the Soil Feels

Ribbon Length

<2.5 cm/1 in

2.5-5 cm/1-2 in

>5 cm/2 in

Gritty

Sandy Loam

Sandy Clay Loam

Sandy Clay

Equally Gritty and Smooth

Loam

Clay Loam

Clay

Smooth

Silty Loam

Silty Clay Loam

Silty Clay

2) Soil Texture Jar Test

After five days, the soil in the jar has settled to show 50% sand, 40% silt and 10% clay.

This simple jar test can help determine the composition of your soil.

• Fill a jar two-thirds full with clean water.
• Dig down below your topmost layer of dirt to get a soil sample. Choose dirt that is free of weeds and grass.
• Add enough dirt to raise the level of the water in your jar most of the way to the top.
• Cover and shake hard until the particles separate.
• Loosen the jar lid. (Good quality soil is full of microorganisms and can ferment!)

Based on a soil sample of 50% sand, 40% silt and 10% clay, the pyramid shows that the soil is loam.

• Allow the sediment to settle for a minute. Mark the jar to indicate the top of the layer that has settled. This layer, closest to the bottom, is the sand.
• Wait two hours and mark the next layer. The second mark is the silt.
• Wait 5 days or long enough to see fairly clear water at the top. Mark the top layer. The top layer is the clay.

• Measure the height of all your layers of dirt combined (100%).
• Measure the height of each individual layer. Calculate the percentage of sand, silt and clay by dividing the amount of each layer into the total amount of all layers.
• Use the Textural Triangle chart to find out what kind of soil you have!

3) Weeds as Soil Condition Indicators – Look at the Weeds!

Observing weeds and plants that naturally thrive in your growing area can tell you about the fertility, pH, drainage and general condition of your soil.

Weeds move in and take advantage of areas where the land has been disturbed. If you think about why these weeds are there, you’ll begin to see them in a new perspective.

Dandelions have long taproots that break up compacted clay soil, and bring up minerals from the subsoil.

Rather than unwanted invaders to be combated, weeds are simply opportunistic plants that move into unsettled areas. Weeds that grow in infertile areas can actually enhance the soil by concentrating minerals and elements in their roots and structures. For example, dandelions and dock that grow in compacted dirt bring up needed minerals from the subsoil with their long taproots. Sorrel, which grows in acidic conditions, concentrates minerals such as calcium and phosphorus, which make the soil more alkaline. Vetch and clover bring nitrogen to poor-fertility soils.

The minerals and elements concentrated in these weeds are released when they decompose back into the ground. That’s why it’s a good idea to include any weeds you pull (minus seeding heads) in your compost. They are bringing your garden exactly what it needs!

Look at the weeds in your growing area and use this Guide to Weeds to determine what kind of soil you have.

Adding Amendments: How to Change Your Soil

Now that you know what kind of soil you have, you can change it to provide the best conditions for your plants.

Acid “Sour” Soil (pH <7) – To make the soil more alkaline, amend it with agricultural limestone (calcium carbonate), bone meal or eggshells. Dried banana peels and aged manure can also raise soil pH and alkalize the soil.

Dry, Sandy Soil – Keep the area planted to develop humus and to keep the topsoil from drying out. Add compost to bind the sand together and help retain moisture. Wood ashes can also help with water retention, but use them with care because they can burn plants. Wood ashes are highly alkaline.

Wet or Moist Soil – Add compost to improve drainage and prevent erosion. Build raised beds to loosen the growing area and provide aeration. Add gravel at the bottom of beds, under the dirt, to assist with drainage.

Straw and grass make good mulch. Coffee grounds can help acidify alkaline soil.

Compacted, Crusty, Clay Soil – Add generous amounts of compost and organic matter to help break up the clay and improve drainage. Cover the surface with topsoil to help plants root. Aerate compacted areas with a broadfork. Build raised beds to loosen the soil and provide aeration.

Low Fertility Soil – Add organic matter, compost and natural fertilizers such as aged manure and chopped leaves. Plant cover crops such as clover, rye or peas, and turn them under to improve fertility.

You mention the three inorganic soil components, but you left out organic material!

In the standard “shake test,” the organics will be on top, and will range from a few percent on soil that has been intensively chemically farmed to 14% or more for land that has been continuously improved over years by the addition of manures (green or animal).